The present invention teaches a horseshoe including a plurality of calks or projecting lugs for enhancing shoe traction. The calks are located on a downwardly facing sloped interior wall of the horseshoe. Each calk comprises an elongated member having a rounded shape on the leading end for permitting the horseshoe to slide forward during the braking or hoof planting phase of the gait cycle. Further, each calk has a grab surface on the rear end side that provides a reaction surface for enhancing traction during the propulsive or thrust phase of the gait cycle. Accordingly, the horseshoe of the present invention can reduce the magnitude of the shock loads experienced by a horse during the hoof planting or braking phase, and improve traction during the propulsive or thrust phase of the gait cycle.
Prior patent references have recited and shown the inclusion of calks, grabs, or other protrusions on the ground engaging side of a horseshoe for enhancing traction. The configuration of these horseshoes are often such that the calks project from the bottom surface of the horseshoe in a manner that causes the hoof of a horse to be elevated more than a plane along the bottom of the shoe relative to the ground support surface. This is generally undesirable in the case of a racehorse, as elevation of the hoof can be associated with a high center of gravity and greater instability when running the turns on an oval track. Moreover, the configuration of such calks, grabs, or other protrusions are often such as to cause rapid deceleration and thereby impart high shock loads upon a horse's hoof and leg during the braking or planting phase of the gait cycle.
Other prior patent references disclose horseshoes having a sloped interior wall portion between the position of the shoe toe grab and the fullering grooves and holes for receiving nails, and the inside edge of the horseshoe. Further, some of these references have recited and shown the inclusion of a plurality of calks, grabs, or other protrusions on this sloped interior wall portion or region, such as U.S. Pat. No. 541,956 granted to J. Benfield in 1895, and also UK Patent Application 2,124,466A by James Wilson published in 1984. In this regard, the amount of drag and traction produced by the calk structures in a horseshoe made in accordance with U.S. Pat. No. 541,956 to Benfield would be relatively equal whether the horseshoe would be sliding forward during the braking phase, or whether the horseshoe would be being driven rearward during the propulsive or thrust phase of the gait cycle. In contrast, the amount of drag and traction produced by the calk structures associated with a horseshoe made in accordance with UK 2,124,466A by Wilson, would be less when the horseshoe would be sliding forwards during the braking phase, and greater during the propulsive phase of the gait cycle. However, not unlike a human being, the heel portion a horse's hoof normally makes the initial contact with the ground support surface during hoof strike or planting, and the toe portion is then lowered to the support surface. During the subsequent propulsive or thrust phase of the gait cycle, the heel portion of the hoof is then the first portion to be lifted from the support surface. In this regard, the projections or calks present on the rear portion of the horseshoe taught in UK 2,124,466A by Wilson can cause the horseshoe to snag or grab the ground support surface during the braking or hoof planting phase of the gait cycle more suddenly than is desired due to the sharp leading edges and generally transverse orientation of the projections or calks recited and shown therein. This can have a number of undesirable side effects such as decreasing a horse's effective stride length and speed, increasing the shock loads imparted to a horse, and causing biomechanical changes with respect to footpath during the gait cycle which can adversely affect the running economy of a horse, particularly a race horse.
Accordingly, it is an object of the present invention to provide a horseshoe including a plurality of projections or calks which do not substantially increase the elevation of a horse's hoof with respect to dirt or grass support surfaces. Further, it is an object of the present invention to provide a horseshoe including a plurality of calks having a grab surface on their rear side for reacting the rearward forces or thrust on the thrust phase against the support surface for enhancing traction during the propulsive or thrust phase of the gait cycle.